Recently, social concern has been increased against global environment problems, such as global warming. Activities for the global environment problems have become one of important social missions for automotive related companies, in addition to activities for improvements of automotive safety. In view of the above problems, it is under review to provide such services, according to which points are given to a vehicle driver depending on driver's contributions to traffic safety, the global environment problems, and so on. And a ranking of the drivers, discounts when buying a new car, and other services are provided to the driver depending on an accumulating total of the points. It is necessary to determine how much the driver's behavior has been contributing to the traffic safety and the global environment problems, when the above services will be provided. The following diagnoses may be possible to determine the above driver's contribution; that is, a diagnosis for determining whether driver's steering operating was smoothly done, a diagnosis for determining whether the driver drove the vehicle safely on a curved road, a diagnosis for determining whether sudden acceleration was not done, a diagnosis for determining whether a braking operation was suddenly carried out, and so on.
The above diagnoses may be carried out by determining whether vehicle acceleration in a vehicle longitudinal direction or in a vehicle transverse direction exceeds a predetermined value. The vehicle acceleration may be a detected value (that is, an output value) of an acceleration sensor mounted in a vehicle for a navigation apparatus. In the case that the navigation apparatus having the acceleration sensor is mounted in the vehicle in an inclined condition with respect to a horizontal line, errors may be generated in an output value of the acceleration sensor due to gravity.
Accordingly, the navigation apparatus defines the vehicle acceleration through correction for the output value of the acceleration sensor by taking the inclination of the navigation apparatus into consideration. Even if the output value of the acceleration sensor is corrected in the case that the navigation apparatus is mounted in the vehicle in the inclined condition, errors may be still generated in the detected value of the acceleration sensor due to influence of acceleration in the vertical direction, which would be caused by vibration in the vertical direction when the vehicle runs on a punishing road. Furthermore, even if the navigation apparatus is mounted in the vehicle in a horizontal condition, errors may be still generated in the detected value of the acceleration sensor due to gravity, when the vehicle runs on a sloping road.
Accordingly, it is necessary to determine whether any errors are generated in the detected value of the acceleration sensor, in order to accurately carry out a certain vehicle control process for vehicle operation, such as a diagnosing process for vehicle behavior performed by a vehicle driver, based on vehicle acceleration.
Japanese Patent Publication No. 2001-328580 (hereinafter referred to as a first patent publication) discloses an automatic transmitting apparatus for a traffic accident, according to which an occurrence of a traffic accident of a motor cycle is detected without using an acceleration sensor. According to the automatic transmitting apparatus of the first patent publication, a control portion determines that the accident has occurred for the motor cycle, when an inclination angle (having an angle larger than a predetermined value) detected by an inclination sensor mounted on the motor cycle is continuously outputted for a period more than a predetermined value. Then, the automatic transmitting apparatus transmits information of a possible accident to a predetermined traffic information center. However, the first patent publication does not disclose a method for determining whether there is an error generated in a detected value for vehicle acceleration, which is outputted from an acceleration sensor.
Japanese Patent Publication No. 2007-246076 (hereinafter referred to as a second patent publication) discloses a movement control apparatus for controlling vehicle behavior and so on. The movement control apparatus prohibits its control, when an inclination of the apparatus with respect to a horizontal line is changed from an initial position, and informs a vehicle driver that a position of the apparatus mounted in a vehicle is not in a good condition.
According to the movement control apparatus according to the second patent publication, it is regarded that error may be generated in detected amount of acceleration, when the inclination of the apparatus is changed from the initial position. Then, the control to be carried out by the movement control apparatus is prohibited. However, the movement control apparatus can not stop its control, when error is generated in the detected amount, for example, in the detected acceleration, due to reasons other than the inclination of the apparatus. For example, when a vehicle is running on a punishing road and thereby vibration is generated in the vertical direction, or when the vehicle is running on a sloping road, the movement control apparatus does not prohibit its control function.